RESPIRATORY METABOLISM OF TILAPIA MOSSAMBICA (TELEOSTEI) .I. EFFECT OF SIZE TEMPERATURE AND SALINITY

In a series of experiments 174, 120 and 139 individuals of the teleost Tilapia mossambica (Peters), were acclimated to 30°C and to salinities of 0.4, 12.5 and 30.5‰, respectively. The effect of temperature and salinity upon oxygen consumption was studied by abruptly transferring fish of different wet weights to temperatures from 15° to 40°C at an average initial pO2 of 250mm Hg. At each salinity, the proportionate response to temperature is size-independent. The metabolic rate increases as a function of temperature at 15° and 30°C but not at 40°C. Oxygen consumption is, however, salinity dependent; maximum rates are obtained at 12.5‰S. This salinity is isotonic in the 80 g fish and, to a lesser extent, in the 5 g fish. Reduction in osmotic load is suggested as the probable cause for a greater scope for activity and greater rate of oxygen consumption in 12.5‰ salinity. © 1969 Springer-Verlag.